linux-kernel - Re: [PATCH] f2fs: fix the assign logic of iocb

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Date:   Thu, 20 Oct 2022 14:57:39 +0530
From:   Mukesh Ojha <quic_mojha@...cinc.com>
To:     Chao Yu <chao@...nel.org>, <jaegeuk@...nel.org>,
        <mhiramat@...nel.org>
CC:     <linux-f2fs-devel@...ts.sourceforge.net>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] f2fs: fix the assign logic of iocb

Hi,

On 10/20/2022 2:31 PM, Chao Yu wrote:
> On 2022/10/20 0:17, Mukesh Ojha wrote:
>> commit 18ae8d12991b ("f2fs: show more DIO information in tracepoint")
>> introduces iocb field in 'f2fs_direct_IO_enter' trace event
>> And it only assigns the pointer and later it accesses its field
>> in trace print log.
>>
>> Fix it by correcting data type and memcpy the content of iocb.
> 
> So the implementation below is wrong, right? since it just assign 
> __entry->name
> with dentry->d_name.name rather than copyiny entirely, so that, during 
> printing

I think, yes.

About the patch, we were getting error as below on doing

echo 51200 > /d/tracing/buffer_size_kb
echo 1 > /d/tracing/events/f2fs/f2fs_direct_IO_enter/enable
echo 1 > /d/tracing/tracing_on
cat /d/tracing/trace_pipe > ftrace.log

Run something which exercise this path.

Unable to handle kernel paging request at virtual address ffffffc04cef3d30
Mem abort info:
ESR = 0x96000007
EC = 0x25: DABT (current EL), IL = 32 bits

  pc : trace_raw_output_f2fs_direct_IO_enter+0x54/0xa4
  lr : trace_raw_output_f2fs_direct_IO_enter+0x2c/0xa4
  sp : ffffffc0443cbbd0
  x29: ffffffc0443cbbf0 x28: ffffff8935b120d0 x27: ffffff8935b12108
  x26: ffffff8935b120f0 x25: ffffff8935b12100 x24: ffffff8935b110c0
  x23: ffffff8935b10000 x22: ffffff88859a936c x21: ffffff88859a936c
  x20: ffffff8935b110c0 x19: ffffff8935b10000 x18: ffffffc03b195060
  x17: ffffff8935b11e76 x16: 00000000000000cc x15: ffffffef855c4f2c
  x14: 0000000000000001 x13: 000000000000004e x12: ffff0000ffffff00
  x11: ffffffef86c350d0 x10: 00000000000010c0 x9 : 000000000fe0002c
  x8 : ffffffc04cef3d28 x7 : 7f7f7f7f7f7f7f7f x6 : 0000000002000000
  x5 : ffffff8935b11e9a x4 : 0000000000006250 x3 : ffff0a00ffffff04
  x2 : 0000000000000002 x1 : ffffffef86a0a31f x0 : ffffff8935b10000
  Call trace:
   trace_raw_output_f2fs_direct_IO_enter+0x54/0xa4
   print_trace_fmt+0x9c/0x138
   print_trace_line+0x154/0x254
   tracing_read_pipe+0x21c/0x380
   vfs_read+0x108/0x3ac
   ksys_read+0x7c/0xec
   __arm64_sys_read+0x20/0x30
   invoke_syscall+0x60/0x150
   el0_svc_common.llvm.1237943816091755067+0xb8/0xf8
   do_el0_svc+0x28/0xa0

-Mukesh